In the technical field of lighting devices, optoelectronic sources such as LED sources to a greater extent, and laser sources to a lesser extent, are becoming more widely used to replace traditional incandescence sources. This involves advantages in terms of energy consumption and maintenance costs. In fact, the optoelectronic sources have lower power consumption than those of incandescence lamps, and they have a service life that is longer than incandescence lamps.
Generally, due to emitted optical power needs, in order to replace an incandescence source, it is necessary to provide an array of optoelectronic sources. Since optoelectronic sources are spatially distributed in the array, in some cases it is not easy or feasible to use optoelectronic sources. Therefore, in such cases, it is necessary use traditional optical incandescence sources. This occurs, for example, but not exclusively, in lighting devices with prevailing lateral emission that are employed as marker lights, lighthouse lamps and lamps for maritime signalling. In such lighting devices, an incandescence lamp that is punctiform, or substantially punctiform, or generally spatially concentrated, is generally provided. Such an incandescence lamp has an omnidirectional radiation diagram. For this reason a collimating lens is generally provided such as a Fresnel lens which is suitable for modifying the radiation diagram so that marker lights have, on the whole, desired directionality characteristics. Traditional incandescence sources, however, have high energy consumption and maintenance costs.